(a) Field of the Invention
The present invention relates to an oil pump of an engine. More particularly, the present invention relates to an oil pump that provides a balancing function for the engine crankshaft.
(b) Description of the Related Art
A crankshaft is precisely designed to balance vibration that may be caused by a reciprocal movement of the pistons. In order to balance vibration, the crankshaft is provided with a balance weight at an opposite side to a crank arm.
Even if vibration of the engine is primarily absorbed by the balance weight of the crankshaft, vibration may not be fully removed thereby. Therefore, in order to balance the remaining vibration of the engine, the engine is typically provided with a flywheel at a side of the crankshaft and a vibration damper of another side thereof. In addition, an engine may be further provided with a balance shaft module that (BSM) that may further balance the remaining vibration.
The balance shaft module typically includes two shafts in parallel. A first shaft of the two balance shafts is usually provided with a sprocket driven by the crankshaft through a gear or a chain. A second shaft of the two shafts is usually externally meshed with the first one by external gears such that the second shaft is driven by the first shaft. Each of the two shafts is provided with a balance weight, i.e., a weight that makes the shaft out of balance, such that the vibration of the engine may be balanced by the rotation of the two shafts.
But with such a complex balance shaft module installed in the engine, the engine becomes bigger in size, and a production cost may increase. Therefore, if balancing of vibration may be accomplished by a simpler scheme, a higher power may be derived from a smaller engine with less vibration, and a production cost may be reduced.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.